Yes. If any VueScan settings are set to Auto, the program recalculates the preview using only the currently selected crop area.

That means when you crop out large bright or dark regions, VueScan’s auto exposure/brightness/color logic uses the smaller selection as its reference. The result can look brighter, darker, or have different color balance because the software is trying to normalize the selected area rather than the full scan bed.

It does this to optimize the scan for the subject you actually want, not the unused background around it.

If you want the display to stay closer to the originally scanned values, turn off automatic correction settings and use manual values instead. In general, any setting left on Auto can cause the image to change when the crop area changes.